The thermal air flow meter that can directly detect air volume has become the mainstream air flow meter. In particular, a thermal air flow meter provided with a measurement device produced by semiconductor micromachining has attracted interest as a low-cost, low-power-consumption air flow meter. For example, PTL 1 proposes a measurement device (thermal air flow sensor) for use in such thermal air flow meters. The thermal air flow sensor proposed by this publication includes an electrically insulating film formed on a semiconductor substrate, heating resistors and resistance temperature detectors formed on the electrically insulating film, and an electrical insulator formed on the heating resistors and the resistance temperature detectors. The heating resistor and resistance temperature detector region has a diaphragm structure formed by removing a portion of the semiconductor substrate from the back side by anisotropic etching.